The present invention relates to liquid crystal devices such as a liquid crystal panel and a manufacturing method and apparatus therefor.
Among conventional manufacturing methods of liquid crystal devices such as a liquid crystal panel, the injection method is well known. In the injection methods, an empty panel is formed by bonding and fixing to each other, with a sealing material, peripheral portions of a pair of substrates that are opposed to each other with a predetermined gap of 1-10 .mu.m. Then, after the empty panel is accommodated in a vacuum apparatus, the inside of the panel is rendered in a vacuum state and an injection opening that is formed in advance in the sealing material portion is immersed in a liquid crystal. Thereafter, by slowly returning the pressure of the inside of the vacuum apparatus to the atmospheric pressure, the liquid crystal is injected into the panel by utilizing the panel inside/outside pressure difference and the capillary action. However, the injection method has a problem that it takes long time to inject a liquid crystal which has a relatively high viscosity. In particular, the injection time increases with the size of a liquid crystal device. There are additional problems that a preprocessing time is needed to render the inside of the vacuum apparatus in a vacuum state, and that an expensive vacuum apparatus is needed. That is, the conventional injection method has the problems of a long manufacturing time and a high cost.
In view of the above, a new method called a dropping method or a coating method has been proposed as disclosed in Japanese Unexamined Patent Publication Nos. Sho. 60-75817, Sho. 60-230636, Hei. 1-303414, Hei. 3-25416, and Hei. 4-218027. In this method, first, a sealing material is applied to one of a pair of substrates to as to surround a display area. After a liquid crystal is dropped on or applied to the display area, the other substrate is pressure-bonded to the one substrate in a vacuum apparatus so that they are rendered parallel with each other and the sealing material is then cured. This method can greatly shorten the time required for the liquid crystal injection. However, because the substrates need to be laid one on another in a vacuum, this method still has the problems that a preprocessing time is needed to render the inside of the vacuum apparatus in a vacuum state and that an expensive vacuum apparatus is needed. That is, this method also has the problems of a long manufacturing time and a high cost.
Japanese Unexamined Patent Publication Nos. Hei. 2-84616, Hei. 2-123324, and Hei. 6-208097 disclose another method in which in the above dropping or coating method the substrates are laid one on another in the air. Because no vacuum apparatus is needed, this method can reduce the manufacturing time and the cost from the case of the dropping method or coating method using a vacuum apparatus. However, in this method, because the substrates are laid one on another in the air, air bubbles may remain in the liquid crystal in the display area during the substrates combining operation, to become display defects. This causes a problem of a reduction in yield.
To solve the problem of residual air bubbles, various methods have been proposed. For example, Japanese Unexamined Patent Publication No. Hei. 3-89315 discloses a method in which a liquid crystal is applied in a predetermined pattern, i.e., in thin lines, and substrates are laid one on another slowly or intermittently. Japanese Unexamined Patent Publication No. Hei. 4-179919 discloses a method in which a pair of substrates are opposed to each other to form a wedge shape or so that one of the substrates is warped to assume a convex shape, and the substrates are pressure-bonded to each other in such a manner that they gradually approach each other and are finally rendered parallel with each other. However, in these methods, the substrates combining operation takes long time and a special device is needed to laying the substrates one on another accurately. Thus, these methods still have the problems of a long manufacturing time and a high cost.